This invention relates generally to improvements in electrostatic filters for filtering and rejuvenating contaminated fluids, such as oils and the like, and more particularly, to improved filters which are easier to manufacture.
Basic structures for removing finite particles by systems employing electrostatic or magnetic means are well known in the art. For examples of such systems, see the following patents:
______________________________________ U.S. Pat. No. ______________________________________ Dawson, et al. 4,961,845 10-9-90 Scott, et al. 4,941,959 7-17-90 Hirama 4,935,133 6-19-90 Eggerichs 4,879,045 11-7-89 Pera 4,716,024 12-29-87 Scott, et al. 4,767,515 8-30-88 Mintz, et al. 4,634,510 1-6-87 Nozawa, et al. 4,620,917 11-4-86 Panson, et al. 4,594,215 6-10-86 Thompson 4,594,138 6-10-86 Collins 4,303,504 12-1-81 Stegelman 4,285,805 8-25-81 Robinson 4,254,393 3-3-81 Wolf 4,238,326 12-9-80 Watson 4,190,524 2-26-80 Noland, et al. 4,025,432 5-24-77 Davies 3,655,550 4-11-72 Van Vroonhoven 3,484,362 12-16-69 Lochmann, et al. 3,398,082 8-20-68 Waterman, et al. 3,393,143 7-68 Miyata 3,349,143 10-24-67 Griswold 3,252,885 5-24-66 Polish Patent 45457 2-24-62 ______________________________________
From this prior art, it is clear that the filtration and effectiveness of a filter is improved by a sue of either or both electrostatic and magnetic force fields.
Such electrostatic and magnetic filters have become quite popular in recent years, especially to filter oils or other petroleum products and provide alternatives to purchasing new fluids after the original supply becomes contaminated. Furthermore, environmental concerns regarding the disposal of used, contaminated fluids has led many users to seek methods for filtering and rejuvenating those fluids.
Many different configurations of electrostatic or magnetic filters have been employed in the past. The patent of Miyata, U.S. Pat. No. 3,349,354, generally discloses a device for treating hydrocarbon fuels with both electric and magnetic fields. Specifically, this patent discloses the use of rod or bar magnets to generate a magnetic field, and of another rod to generate an electric field. It is unclear if this device has any filtering properties.
The patent of Lochmann, et al., U.S. Pat. No. 3,398,082, discloses a method for electrostatic filtration of dielectric fluids by using a plurality of alternatively charged electrostatic perforated plates. However, Lochmann, et al do not contemplate the addition of a magnetic field along with the electrostatic fields generated by the perforated plates. The patent of Van Vroonhoven, U.S. Pat. No. 3,484,362, also discloses the use of a dielectric filter media disposed between adjacent electrostatic elements inside the filter. This patent does not use magnetic field either.
The patent of Robinson, U.S. Pat. No. 4,254,393, discloses the use of both electric and magnetic fields to treat a hydrocarbon fuel. This patent does not contemplate either a serial alternation of areas bearing different charges or serial alternation of those areas with magnetic areas. Also, it is not clear that this U.S. Pat. No. 4,254,393 has any filtration effects.
The current market for fluid filters for use with fluids and the like is vast and demanding. The machines which these filters service are made with high precision and generally require fluids that are substantially free of contaminants. Due to the costly operation and repair of these machines, it is necessary that these filters perform their functions with extreme accuracy. Further, depending on the particular fluid that is being filtered, it may be necessary to target specific contaminants for removal. Filters should also be able to remove contaminants of small size, for example in the order of five microns or less in diameter. Also, filters employed in heavy industry need a control system that can effectively monitor the operation of the filter.
The filter system shown in the parent application Ser. No. 07/632,129 is a very good design; however, it is more costly to manufacture than might be reasonably expected. Also, there are expansion gaps which contain conductive strips which may cause problems under some circumstances.
Various fluids have different electrical conductive or magnetic responsive characteristics. Thus, the electrical or magnetic fields that are built up inside the filter should have different characteristics depending upon the characteristics of the fluid being filtered. It has been found that, for any given fluid or fluids, tests may be run in order to discover the nature of fields which best serve the needs of those fluids. Once the test data is available for a number of fluids, a data base may be established which will provide the specifications of a filter for a new and unknown fluid.
Accordingly, a filter should have a design which enables it to be configured different ways to meet the needs of new fluids. It would appear that an ideal filter design would be one which the same parts may be assembled in different ways to accommodate different fluids.